1. Field of the Invention
The present invention relates to a steam turbine plant, for example, using solar heat.
2. Background Art
FIG. 5 is a schematic diagram illustrating an example of a conventional steam turbine plant using solar heat. A steam turbine cycle of the plant of FIG. 5 will be described.
A heating medium 118 is transferred to a solar energy collector 119 collecting solar heat by a heating medium pump 116. The heating medium 118 is, for example, oil. The heating medium 118 is heated by radiant heat of a solar ray 117 at the solar energy collector 119. Subsequently, the heating medium 118 is transferred to a heater 110 as a heat exchanger, and a heating object such as water or steam is heated therein. The temperature of the heating medium 118 decreases at the heater 110, and returns to the upstream of the heating medium pump 116. In this way, the heating medium 118 circulates.
In the nighttime when the solar ray 117 may not be received or in the weather of daytime when the solar ray 117 is weak, the heating medium 118 accumulated in a heat accumulating tank is circulated or the heating medium 118 is circulated to a line heated by an auxiliary boiler. However, the devices or the flow thereof are not shown herein. Meanwhile, in this case, the heating medium 118 bypasses the solar energy collector 119.
As the solar energy collector 119, various types may be used, but a trough condensing type shown in FIG. 8 is used in many cases. FIG. 8 is a schematic diagram illustrating an example of the trough condensing type solar energy collector 119. The solar energy collector 119 of FIG. 8 condenses the solar ray 117 by a collector mirror 123 and heats a solar energy collection pipe 124. The heating medium 118 circulates in the solar energy collection pipe 124, and the temperature of the heating medium 118 increases by radiant heat transmitted from the solar ray 117 to the solar energy collection pipe 124. The upstream and the downstream of the solar energy collection pipe 124 are respectively connected to heating medium pipes 125. Although the solar energy collection pipe 124 is made by the careful examination, the pipe will not be described herein in detail.
Hereinafter, returning to FIG. 5, the description of the steam turbine plant will be continued.
In many cases, the conventional steam turbine cycle is configured as a single-stage reheating cycle that includes a high pressure turbine 101 and a reheat turbine. An intermediate pressure turbine 102 and a low pressure turbine 103 are treated as a continuous reheat turbine 113.
The heater 110 includes a boiler 108 which changes water 111 into steam 112 by the heat of the heating medium 118, and a reheater 109 which heats steam for the reheat turbine 113. The water 111 is transferred to the boiler 108 as a part of the heater 110 by the pump 105, and is heated by the boiler 108 so that the water changes into high pressure turbine inlet steam 112. In FIG. 5, the inlet at the most upstream of the high pressure turbine 101 is denoted by the symbol X.
The high pressure turbine inlet steam 112 flows into the high pressure turbine 101 and expands inside the high pressure turbine 101 so that the pressure and the temperature thereof decrease. The high pressure turbine 101 is driven by the high pressure turbine inlet steam 112. In the steam turbine cycle using solar heat, the temperature of the high pressure turbine inlet steam 112 is lower than that of the steam turbine cycle using heat of combusted exhaust gas of fuel in many cases. For this reason, the high pressure turbine exhaust 114 is not all dry steam as gas, but is partly mixed with a liquid. That is, it is humid steam in which the dryness degree is less than 1.
In FIG. 5, a high pressure turbine steam outlet (an exhaust port) located at the most downstream of the high pressure turbine 101 is denoted by the symbol Y. The high pressure turbine exhaust 114 flows into the reheater 109 as a part of the heater 110, is heated by the heat of the heating medium 118, and flows into the intermediate pressure turbine 102.
Intermediate pressure turbine inlet steam 106 expands inside the intermediate pressure turbine 102 so that the pressure and the temperature thereof both decrease and flows into the low pressure turbine 103. The steam flowing into the low pressure turbine 103 expands inside the low pressure turbine 103 so that the pressure and the temperature both decrease and the steam flows to the outside as humid steam. In this way, the intermediate pressure turbine 102 and the low pressure turbine 103 are driven as well as the high pressure turbine 101.
The steam flowing from the low pressure turbine 103, that is, low pressure turbine exhaust 115 flows into a condenser 104. In the condenser 104, the low pressure turbine exhaust 115 is cooled by cooling water, and is returned to the water 111. The water 111 returns to the upstream of the pump 105. In this way, the water 111 and the steam 112 circulate. Meanwhile, seawater or stream water may be used as the cooling water, the water warmed at the condenser 104 may be cooled at a cooling tower using atmosphere, and the cooled water may be circulated.
The rotation shafts of the high pressure turbine 101, the intermediate pressure turbine 102, and the low pressure turbine 103 are connected to a power generator 107. The rotation shafts thereof are rotated as the high pressure turbine 101, the intermediate pressure turbine 102, and the low pressure turbine 103 are rotated by the expanding steam. By the rotation of the rotation shafts, power is generated in the power generator 107.
FIG. 6 is a schematic diagram illustrating another example of the conventional steam turbine plant using solar heat.
In FIG. 6, extraction steam 120 is extracted from one or more turbines among the high pressure turbine 101, the intermediate pressure turbine 102, and the low pressure turbine 103. A feed-water heater 121 using the extraction steam 120 as a heat source is provided between the condenser 104 and the boiler 108, and the water 111 is heated at the feed-water heater 121. In FIG. 6, the extraction port of the high pressure turbine 101 is denoted by the symbol Z. The number of the feed-water heaters 121 may be one or more (three heaters are shown in FIG. 6), and the extraction steam 120 may be supplied from one turbine to the plurality of feed-water heaters 121.
Likewise, the steam turbine cycle of the plant of FIG. 6 includes the reheating cycle and the reheat regeneration cycle as a regeneration cycle, and the conventional steam turbine cycle has that configuration in many cases. The cycle efficiency is improved by the effect of the regeneration cycle. The extraction steam 120 is cooled at the feed-water heater 121 so that the steam changes into water and is merged with the water 111 at a drain water pump 122. Meanwhile, in FIG. 6, the description of the flow of the heating medium 118 is omitted.
FIG. 7 is a diagram illustrating an example of an expansion line of the conventional steam turbine plant shown in FIG. 5 or 6. In FIG. 7, the vertical axis indicates specific enthalpy, and the horizontal axis indicates specific entropy.
In FIG. 7, a high pressure turbine expansion line 201, a reheat turbine expansion line 202, and a saturation line 203 are shown. Since the intermediate pressure turbine 102 and the low pressure turbine 103 are the continuous reheat turbine, the expansion line related to the turbine is one expansion line.
In FIG. 7, a high pressure turbine inlet point 204, a high pressure turbine outlet point 205, a reheat turbine inlet point (an intermediate pressure turbine inlet point) 206, and a reheat turbine outlet point (a low pressure turbine outlet point) 207 are shown.
In FIG. 7, the high pressure turbine exhaust 114 is heated at the reheater 109 up to a temperature equal to that of the high pressure turbine inlet steam 112. Further, in FIG. 7, when the steam changes from the high pressure turbine inlet point 204 to the high pressure turbine outlet point 205 or changes from the reheat turbine inlet point 206 to the reheat turbine outlet point 207, the steam changes more than the saturation line 203. Therefore, the steam is dry steam at the high pressure turbine inlet point 204 or the reheat turbine inlet point 206, and the steam is humid steam at the high pressure turbine outlet point 205 or the reheat turbine outlet point 207.
Meanwhile, JP-A 2008-39367 (KOKAI) describes an example of a solar power generation facility that includes a solar energy collection device heating a liquid thermal medium by the solar ray.